Tungsten film-forming method, film-forming system and storage medium

ABSTRACT

There is provided a tungsten film-forming method, including: forming a silicon film on a substrate in a reduced pressure atmosphere by disposing the substrate having a protective film formed on a surface of the substrate in a processing container; forming an initial tungsten film by supplying a tungsten chloride gas to the substrate having the silicon film formed thereon; and forming a main tungsten film by supplying a tungsten-containing gas to the substrate having the initial tungsten film formed thereon.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Divisional Application of U.S. patent application Ser. No.16/276,867, filed Feb. 15, 2019, an application claiming benefit fromJapanese Patent Application No. 2018-029006, filed on Feb. 21, 2018, theentire contents of each of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a tungsten film-forming method, afilm-forming system and a storage medium.

BACKGROUND

In LSI, tungsten is widely used for parts requiring a heat resistance,such as a MOSFET gate electrode, a contact with a source/drain, a wordline of a memory and the like. In recent years, a chemical vapordeposition (CVD) method with good step coverage is used for a depositionprocess of tungsten.

In the related art, when forming a tungsten film by the CVD method, fromthe viewpoint of adhesion to a silicon layer and suppression of areaction, there has been used a method in which a TiN film is formed asa barrier layer on a silicon layer and a tungsten film is formed on theTiN film. Furthermore, in the related art, a nucleation process forfacilitating uniform tungsten film formation is performed prior to mainfilm formation of the tungsten film by the above reaction.

SUMMARY

Some embodiments of the present disclosure provide a technique capableof reducing the resistance of a tungsten film.

According to one embodiment of the present disclosure, there is provideda tungsten film-forming method, including: forming a silicon film on asubstrate in a reduced pressure atmosphere by disposing the substratehaving a protective film formed on a surface of the substrate in aprocessing container; forming an initial tungsten film by supplying atungsten chloride gas to the substrate having the silicon film formedthereon; and forming a main tungsten film by supplying atungsten-containing gas.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentdisclosure, and together with the general description given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present disclosure.

FIG. 1 is a diagram showing an example of a schematic overallconfiguration of a film-forming system according to an embodiment of thepresent disclosure.

FIG. 2 is a sectional view showing an example of a schematicconfiguration of a first film-forming apparatus according to anembodiment of the present disclosure.

FIG. 3 is showing an example of a schematic configuration of a secondfilm-forming apparatus according to an embodiment of the presentdisclosure.

FIG. 4 is a flowchart showing an example of a flow of respective stepsof a film-forming method according to an embodiment of the presentdisclosure.

FIGS. 5A to 5D are sectional views schematically showing an example ofthe states of a wafer in the respective steps of the film-forming methodaccording to an embodiment of the present disclosure.

FIG. 6 is a diagram showing an example of a gas supply sequence at thetime of forming a silicon film according to an embodiment of the presentdisclosure.

FIG. 7 is a diagram showing an example of a gas supply sequence at thetime of forming an initial tungsten film according to an embodiment ofthe present disclosure.

FIG. 8 is a diagram showing an example of a layer configuration of awafer according to an embodiment of the present disclosure.

FIG. 9 is a diagram showing an example of a layer configuration of awafer according to a comparative example.

FIG. 10 is a diagram showing an example of a change in resistivity withrespect to a thickness of a tungsten film.

FIG. 11 is a sectional view showing another example of the schematicconfiguration of the film-forming apparatus according to an embodimentof the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present disclosure. However,it will be apparent to one of ordinary skill in the art that the presentdisclosure may be practiced without these specific details. In otherinstances, well-known methods, procedures, systems, and components havenot been described in detail so as not to unnecessarily obscure aspectsof the various embodiments.

Hereinafter, embodiments of a tungsten film-forming method and afilm-forming system of the present disclosure will be described indetail with reference to the drawings. In the drawings, the same orcorresponding parts are designated by like reference numerals. Inaddition, the technique disclosed herein is not limited by theembodiments.

[System Configuration]

In the present embodiment, a case where film formation is performed by afilm-forming system including a plurality of film-forming apparatuseswill be described as an example. First, a film-forming system accordingto the present embodiment will be described. FIG. 1 is a diagram showingan example of a schematic overall configuration of a film-forming systemaccording to an embodiment. The film-forming system 100 is configured toform a tungsten film by forming a silicon film on a substrate having aprotective film, for example, an AlO film formed on a surface thereof,replacing the silicon film to form an initial tungsten film, and forminga main tungsten film on the initial tungsten film. In the presentembodiment, a case where the substrate is a silicon wafer will bedescribed by way of example.

As shown in FIG. 1 , the film-forming system 100 includes one firstfilm-forming apparatus 101 for forming a silicon film, one secondfilm-forming apparatus 102 for forming an initial tungsten film, and onethird film-forming apparatus 103 for forming a main tungsten film. Thefirst film-forming apparatus 101, the second film-forming apparatus 102and the third film-forming apparatus 103 are connected to three wallportions of a vacuum transfer chamber 301 having a heptagonal shape in aplan view via gate valves G, respectively. The inside of the vacuumtransfer chamber 301 is evacuated by a vacuum pump and kept at apredetermined degree of vacuum. In other words, the film-forming system100 is a multi-chamber type vacuum processing system, in which atungsten film can be continuously formed without breaking the vacuum.That is, all of the processes performed in the processing containers ofthe first film-forming apparatus 101, the second film-forming apparatus102, and the third film-forming apparatus 103 are performed withoutexposing a silicon wafer W (hereinafter referred to as “wafer W”) to theair.

The configurations of the first film-forming apparatus 101 and thesecond film-forming apparatus 102 will be described later. The thirdfilm-forming apparatus 103 is, for example, an apparatus that forms atungsten film (W) by alternately or simultaneously supplying, forexample, a tungsten-containing gas and a hydrogen-containing gas ontothe wafer W by ALD (Atomic Layer Deposition) or CVD (Chemical VaporDeposition) in a vacuum atmosphere chamber. The tungsten-containing gasis, for example, a WF₆ gas, and the hydrogen-containing gas is, forexample, a H₂ gas.

Three load lock chambers 302 are connected to the remaining three wallportions of the vacuum transfer chamber 301 via gate valves G1. At theopposite side of the vacuum transfer chamber 301 across the load lockchambers 302, an atmospheric transfer chamber 303 is provided. The threeload lock chambers 302 are connected to the atmospheric transfer chamber303 via the gate valves G2. The load lock chambers 302 control apressure between the atmospheric pressure and the vacuum when the waferW is transferred between the atmospheric transfer chamber 303 and thevacuum transfer chamber 301.

Three carrier attachment ports 305 to which carriers (FOUPs or the like)C for accommodating wafers W are attached are provided on the wallportion of the atmospheric transfer chamber 303 opposite to the wallportion to which the load lock chambers 302 are attached. An alignmentchamber 304 for aligning the wafer W is provided on a sidewall of theatmospheric transfer chamber 303. A down-flow of clean air is formed inthe atmospheric transfer chamber 303.

Inside the vacuum transfer chamber 301, a transfer mechanism 306 isprovided. The transfer mechanism 306 transfers the wafer W to the firstfilm-forming apparatus 101, the second film-forming apparatus 102 andthe load lock chambers 302. The transfer mechanism 306 includes twoindependently-movable transfer arms 307 a and 307 b.

Inside the atmospheric transfer chamber 303, a transfer mechanism 308 isprovided. The transfer mechanism 308 is configured to transfer the waferW to the carriers C, the load lock chambers 302 and the alignmentchamber 304.

The film-forming system 100 includes an overall control part 310. Theoverall control part 310 includes a main control part such as a CPU(computer) or the like, an input device (a keyboard, a mouse, etc.), anoutput device (a printer, etc.), a display device (display, etc.), and astorage device (storage medium). The main control part controls therespective constituent parts of the first film-forming apparatus 101 andthe respective constituent parts of the second film-forming apparatus102. Further, the main control part controls an exhaust mechanism, a gassupply mechanism and a transfer mechanism 306 of the vacuum transferchamber 301, an exhaust mechanism and a gas supply mechanism of the loadlock chamber 302, a transfer mechanism 308 of the atmospheric transferchamber 303, a driving system of the gate valves G, G1 and G2, and thelike. The main control part of the overall control part 310 causes thefilm-forming system 100 to perform a predetermined operation, forexample, based on a processing recipe stored in a storage medium builtin the storage device or in a storage medium set in the storage device.The overall control part 310 may be a higher-level control part of thecontrol parts of the respective units, such as the control part 6 of thefirst film-forming apparatus 101 and the second film-forming apparatus102 which will be described later.

Next, the operation of the film-forming system 100 configured asdescribed above will be described. The following processing operation isexecuted based on the processing recipe stored in the storage medium inthe overall control part 310.

First, the carrier C containing wafers W is attached to the carrierattachment port 305 of the atmospheric transfer chamber 303. An AlO filmas a protective layer is formed on the surface of the wafer W. Thetransfer mechanism 308 of the atmospheric transfer chamber 303 takes outthe wafer W from the carrier C and loads it into the alignment chamber304. The alignment chamber 304 performs alignment of the wafer W. In theatmospheric transfer chamber 303, the gate valve G2 of one of the loadlock chambers 302 is opened. The transfer mechanism 308 takes out thealigned wafer W from the alignment chamber 304. The transfer mechanism308 loads the taken-out wafer W into the load lock chamber 302 from theopened gate valve G2. After loading the wafer W, the gate valve G2 ofthe load lock chamber 302 is closed. The load lock chamber 302 intowhich the wafer W has been loaded is evacuated.

When the load lock chamber 302 reaches a predetermined degree of vacuum,the gate valve G1 of the load lock chamber 302 is opened. The transfermechanism 306 takes out the wafer W from the load lock chamber 302 byone of the transfer arms 307 a and 307 b.

The gate valve G of the first film-forming apparatus 101 is opened. Thetransfer mechanism 306 loads the wafer W held by one of the transferarms into the first film-forming apparatus 101 and returns the emptytransfer arm to the vacuum transfer chamber 301. The gate valve G of thefirst film-forming apparatus 101 is closed. The first film-formingapparatus 101 performs a film-forming process of a silicon film on theloaded wafer W.

After completion of the film-forming process of the silicon film, thegate valve G of the first film-forming apparatus 101 is opened. Thetransfer mechanism 306 unloads the wafer W from the first film-formingapparatus 101 by one of the transfer arms 307 a and 307 b. The gatevalve G of the second film-forming apparatus 102 is opened. The transfermechanism 306 loads the wafer W held by one of the transfer arms intothe second film-forming apparatus 102 having the gate valve G opened,and returns the empty transfer arm to the vacuum transfer chamber 301.The gate valve G of the second film-forming apparatus 102 into which thewafer W has been loaded is closed. The second film-forming apparatus 102performs a film-forming process of an initial tungsten film on theloaded wafer W.

After completion of the film-forming process of the initial tungstenfilm, the gate valve G of the second film-forming apparatus 102 isopened. The transfer mechanism 306 unloads the wafer W from the secondfilm-forming apparatus 102 by one of the transfer arms 307 a and 307 b.The gate valve G of the third film-forming apparatus 103 is opened. Thetransfer mechanism 306 loads the wafer W held by one of the transferarms into the third film-forming apparatus 103 with the gate valve Gopened, and returns the empty transfer arm to the vacuum transferchamber 301. The gate valve G of the third film-forming apparatus 103into which the wafer W has been loaded is closed. The third film-formingapparatus 103 performs a film-forming process of a main tungsten film onthe loaded wafer W.

After the main tungsten film is formed, the gate valve G of the thirdfilm-forming apparatus 103 is opened. The transfer mechanism 306 unloadsthe wafer W from the third film-forming apparatus 103 by one of thetransfer arms 307 a and 307 b. The gate valve G1 of one of the load lockchambers 302 is opened. The transfer mechanism 306 loads the wafer W onthe transfer arm into the load lock chamber 302. The gate valve G1 ofthe load lock chamber 302 into which the wafer W has been loaded isclosed. The inside of the load lock chamber 302 into which the wafer Whas been loaded is returned to the atmospheric pressure. The gate valveG2 of the load lock chamber 302 whose inside has been returned to theatmospheric pressure is opened. The transfer mechanism 308 takes out thewafer W in the load lock chamber 302 from the opened gate valve G2. Thetransfer mechanism 308 returns the taken-out wafer W to the carrier C.

The above processes are performed concurrently on a plurality of wafersW, whereby the film-forming process of the tungsten film for apredetermined number of wafers W is completed.

As described above, by constituting the film-forming system 100 with onefirst film-forming apparatus 101, one second film-forming apparatus 102and one third film-forming apparatus, it is possible to realize theformation of the silicon film, the formation of the initial tungstenfilm and the formation of the main tungsten film with high throughput.The film-forming system 100 of the present embodiment is illustrated asa vacuum processing system equipped with three film-forming apparatuses.However, as long as a plurality of film-forming apparatuses can bemounted on a vacuum processing system, the number of film-formingapparatuses is not limited thereto. The number of film-formingapparatuses may be four or more.

[Configuration of Film-Forming Apparatus]

The first film-forming apparatus 101 and the second film-formingapparatus 102 have substantially the same configuration. Hereinafter,the configuration of the first film-forming apparatus 101 will be mainlydescribed. As for the configuration of the second film-forming apparatus102, different parts will be mainly described.

The configuration of the first film-forming apparatus 101 will bedescribed. FIG. 2 is a sectional view showing an example of theschematic configuration of the first film-forming apparatus according tothe present embodiment. The first film-forming apparatus 101 includes aprocessing container 1, a mounting table 2, a shower head 3, an exhaustpart 4, a gas supply mechanism 5 and a control part 6.

The processing container 1 is made of a metal such as aluminum or thelike and has a substantially cylindrical shape. The processing container1 accommodates a wafer W as a substrate to be processed. Aloading/unloading port 11 for loading or unloading the wafer W is formedon the side wall of the processing container 1. The loading/unloadingport 11 is opened and closed by a gate valve 12. An annular exhaust duct13 having a rectangular cross section is provided on the main body ofthe processing container 1. A slit 13 a is formed in the exhaust duct 13along the inner peripheral surface. An exhaust port 13 b is formed inthe outer wall of the exhaust duct 13. On the upper surface of theexhaust duct 13, a top wall 14 is provided so as to close the upperopening of the processing container 1. The space between the exhaustduct 13 and the top wall 14 is hermetically sealed by a seal ring 15.

The mounting table 2 horizontally supports the wafer W in the processingcontainer 1. The mounting table 2 is formed in a disk shape having asize corresponding to the wafer W and is supported by a support member23. The mounting table 2 is made of a ceramic material such as aluminumnitride (AlN) or the like, or a metallic material such as aluminum,nickel alloy or the like. A heater 21 for heating the wafer W is buriedin the mounting table 2. The heater 21 is supplied with electric powerfrom a heater power supply (not shown) to generate heat. Then, an outputof the heater 21 is controlled by a temperature signal of a thermocouple(not shown) provided in the vicinity of the upper surface of themounting table 2, whereby the wafer W is controlled to a predeterminedtemperature. In the mounting table 2, a cover member 22 formed ofceramics such as alumina or the like is provided so as to cover theouter peripheral region of the upper surface and the side surface.

On the bottom surface of the mounting table 2, a support member 23 forsupporting the mounting table 2 is provided. The support member 23extends downward from the center of the bottom surface of the mountingtable 2 through a hole formed in the bottom wall of the processingcontainer 1. The downwardly-extending lower end of the support member 23is connected to an elevating mechanism 24. The mounting table 2 israised and lowered via the support member 23 by the elevating mechanism24 between a processing position shown in FIG. 2 and a transfer positionlocated below the processing position as indicated by a two-dot chainline so that the wafer W can be transferred. A flange portion 25 isattached to the support member 23 on the lower side of the processingcontainer 1. Between the bottom surface of the processing container 1and the flange portion 25, there is provided a bellows 26 which isolatesthe atmosphere inside the processing container 1 from an external airand which expands and contracts in response to the upward/downwardmovement of the mounting table 2.

Three wafer support pins 27 are provided in the vicinity of the bottomsurface of the processing container 1 so as to protrude upward from anelevating plate 27 a. In FIG. 2 , two of the three wafer support pins 27are shown. The wafer support pins 27 are raised and lowered via theelevating plate 27 a by an elevating mechanism 28 provided below theprocessing container 1. The wafer support pins 27 are inserted throughthe through holes 2 a provided in the mounting table 2 located at thetransfer position and can protrude and retract with respect to the uppersurface of the mounting table 2. By moving the wafer support pins 27 upand down, the delivery of the wafer W between the transfer mechanism(not shown) and the mounting table 2 is performed.

The shower head 3 supplies a processing gas into the processingcontainer 1 in a shower shape. The shower head 3 is made of a metal andis provided so as to face the mounting table 2. The shower head 3 hassubstantially the same diameter as the mounting table 2. The shower head3 includes a main body portion 31 fixed to the top wall 14 of theprocessing container 1 and a shower plate 32 connected to a lowerportion of the main body portion 31. A gas diffusion space 33 is formedbetween the main body portion 31 and the shower plate 32. In the gasdiffusion space 33, gas introduction holes 36 and 37 are provided so asto penetrate the top wall 14 of the processing container 1 and thecenter of the main body portion 31. An annular protrusion 34 protrudingdownward is formed in the peripheral edge portion of the shower plate32. Gas discharge holes 35 are formed on the inner flat surface of theannular protrusion 34. In a state in which the mounting table 2 islocated at the processing position, a processing space 38 is formedbetween the mounting table 2 and the shower plate 32, and the uppersurface of the cover member 22 and the annular protrusion 34 come closeto each other to form an annular gap 39.

The exhaust part 4 evacuates the inside of the processing container 1.The exhaust part 4 includes an exhaust pipe 41 connected to the exhaustport 13 b and an exhaust mechanism 42 having a vacuum pump, a pressurecontrol valve and the like connected to the exhaust pipe 41. In aprocess, the gas in the processing container 1 is moved to the exhaustduct 13 via the slit 13 a and is exhausted from the exhaust duct 13through the exhaust pipe 41 by the exhaust mechanism 42.

The gas supply mechanism 5 is connected to the gas introduction holes 36and 37 and is capable of supplying various gases used for filmformation. In the present embodiment, a silicon film is formed on thewafer W by supplying a SiH₄ (silane) gas and a B₂H₆ (boron) gas from thegas supply mechanism 5. By forming the silicon film using the SiH₄ gasand the B₂H₆ gas, it is possible to improve the adhesion of the siliconfilm with respect to the wafer W. The gas used for forming the siliconfilm is not limited to the combination of the SiH₄ and the B₂H₆. Forexample, the gas used for forming the silicon film may be DCS or Si₂H₆.

For example, the gas supply mechanism 5 includes a SiH₄ gas supplysource 51 a, an N₂ gas supply source 52 a, an N₂ gas supply source 53 a,a B₂H₆ gas supply source 55 a, an N₂ gas supply source 56 a and an N₂gas supply source 57 a as gas supply sources for forming a silicon film.In the gas supply mechanism 5 shown in FIG. 2 , the respective gassupply sources are shown separately. However, the gas supply sourcescapable of being used in common may be used in common.

The SiH₄ gas supply source 51 a supplies a SiH₄ gas into the processingcontainer 1 via a gas supply line 51 b. In the gas supply line 51 b, aflow rate controller 51 c, a storage tank 51 d and a valve 51 e areinstalled sequentially from the upstream side. On the downstream side ofthe valve 51 e, the gas supply line 51 b is connected to the gasintroduction hole 36. The SiH₄ gas supplied from the SiH₄ gas supplysource 51 a is temporarily stored in the storage tank 51 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 51 d, and then supplied to the processingcontainer 1. The supply and cutoff of the SiH₄ gas to be supplied fromthe storage tank 51 d to the processing container 1 is performed by thevalve 51 e. By temporarily storing the SiH₄ gas in the storage tank 51 din this manner, the SiH₄ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 52 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 52 b. In the gas supplyline 52 b, a flow rate controller 52 c, a storage tank 52 d and a valve52 e are installed sequentially from the upstream side. On thedownstream side of the valve 52 e, the gas supply line 52 b is connectedto the gas supply line 51 b. The N₂ gas supplied from the N₂ gas supplysource 52 a is temporarily stored in the storage tank 52 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 52 d, and then supplied into the processingcontainer 1. The supply and cutoff of the N₂ to be supplied from thestorage tank 52 d to the processing container 1 is performed by thevalve 52 e. By temporarily storing the N₂ gas in the storage tank 52 din this manner, the N₂ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 53 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 53 b. In the gas supplyline 53 b, a flow rate controller 53 c, a valve 53 e and an orifice 53 fare installed sequentially from the upstream side. On the downstreamside of the orifice 53 f, the gas supply line 53 b is connected to thegas supply line 51 b. The N₂ gas supplied from the N₂ gas supply source53 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 53 a to the processing container1 are performed by the valve 53 e. The gas is supplied to the gas supplyline 51 b at a relatively large flow rate by the storage tanks 51 d and52 d. The gas supplied to the gas supply line 51 b is prevented fromflowing back to the gas supply line 53 b by the orifice 53 f.

The B₂H₆ gas supply source 55 a supplies a B₂H₆ gas into the processingcontainer 1 via a gas supply line 55 b. In the gas supply line 55 b, aflow rate controller 55 c, a storage tank 55 d and a valve 55 e areinstalled sequentially from the upstream side. On the downstream side ofthe valve 55 e, the gas supply line 55 b is connected to the gasintroduction hole 37. A B₂H₆ gas supplied from the B₂H₆ gas supplysource 55 a is temporarily stored in the storage tank 55 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 55 d, and then introduced into theprocessing container 1. The supply and cutoff of the B₂H₆ gas to besupplied from the storage tank 55 d to the processing container 1 areperformed by the valve 55 e. By temporarily storing the B₂H₆ gas in thestorage tank 55 d in this manner, the B₂H₆ gas can be stably suppliedinto the processing container 1 at a relatively large flow rate.

The N₂ gas supply source 56 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 56 b. In the gas supplyline 56 b, a flow rate controller 56 c, a storage tank 56 d and a valve56 e are installed sequentially from the upstream side. On thedownstream side of the valve 56 e, the gas supply line 56 b is connectedto the gas supply line 55 b. The N₂ gas supplied from the N₂ gas supplysource 56 a is temporarily stored in the storage tank 56 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 56 d, and then supplied into the processingcontainer 1. The supply and cutoff of the N₂ gas to be supplied from thestorage tank 56 d to the processing container 1 is performed by thevalve 56 e. By temporarily storing the N₂ gas in the storage tank 56 din this manner, the N₂ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 57 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 57 b. In the gas supplyline 57 b, a flow rate controller 57 c, a valve 57 e and an orifice 57 fare installed sequentially from the upstream side. On the downstreamside of the orifice 57 f, the gas supply line 57 b is connected to thegas supply line 55 b. The N₂ gas supplied from the N₂ gas supply source57 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 57 a to the processing container1 are performed by the valve 57 e. The gas is supplied to the gas supplyline 55 b at a relatively large flow rate by the storage tanks 55 d and56 d. The gas supplied to the gas supply line 55 b is prevented fromflowing back to the gas supply line 57 b by the orifice 57 f.

The operation of the first film-forming apparatus 101 configured asdescribed above is generally controlled by the control part 6. Thecontrol part 6 is, for example, a computer, and includes a CPU (CentralProcessing Unit), a RAM (Random Access Memory), a ROM (Read OnlyMemory), an auxiliary storage device, and the like. The CPU operatesbased on a program stored in the ROM or the auxiliary storage device,and controls the overall operation of the apparatus. The control part 6may be provided inside the first film-forming apparatus 101 or may beprovided outside the first film-forming apparatus 101. When the controlpart 6 is provided outside the first film-forming apparatus 101, thecontrol part 6 can control the first film-forming apparatus 101 by awire or wireless communication means.

Next, the configuration of the second film-forming apparatus 102 will bedescribed. FIG. 3 is a sectional view showing an example of theschematic configuration of the second film-forming apparatus accordingto the embodiment. The second film-forming apparatus 102 has the sameconfiguration as the first film-forming apparatus 101 except for the gasto be used and the gas supply mechanism 5 for supplying the gas. Theparts of the second film-forming apparatus 102 which are the same asthose of the first film-forming apparatus 101 are denoted by likereference numerals, and a description thereof will be omitted. Differentpoints will be mainly described.

The gas supply mechanism 5 is connected to gas introduction holes 36 and37, and is capable of supplying various gases used for film formation.In the present embodiment, a tungsten chloride gas and a hydrogen gasare supplied from the gas supply mechanism 5 to form an initial tungstenfilm on the wafer W. In the present embodiment, a case where a WCl₆ gasis used as tungsten chloride gas is described by way of example.However, a WCl₅ gas may be used. Further, the gas used for forming theinitial tungsten film is not limited to the combination of the tungstenchloride gas and the hydrogen gas. For example, depending on processconditions such as a temperature, a pressure and the like, the initialtungsten film may be formed by only the tungsten chloride gas.

For example, the gas supply mechanism 5 includes a WCl₆ gas supplysource 61 a, an N₂ gas supply source 62 a, an N₂ gas supply source 63 a,a H₂ gas supply source 64 a, a H₂ gas supply source 65 a, an N₂ gassupply source 66 a, and an N₂ gas supply source 67 a as a gas supplysource of a gas for forming the initial tungsten film. Even in the gassupply mechanism 5 shown in FIG. 3 , the respective gas supply sourcesare separately shown. However, the gas supply sources capable of beingused in common may be used in common.

The WCl₆ gas supply source 61 a supplies a WCl₆ gas into the processingcontainer 1 via a gas supply line 61 b. In the gas supply line 61 b, aflow rate controller 61 c, a storage tank 61 d and a valve 61 e areinstalled sequentially from the upstream side. On the downstream side ofthe valve 61 e, the gas supply line 61 b is connected to the gasintroduction hole 36. The WCl₆ gas supplied from the WCl₆ gas supplysource 61 a is temporarily stored in the storage tank 61 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 61 d, and then supplied into the processingcontainer 1. The supply and cutoff of the WCl₆ gas to be supplied fromthe storage tank 61 d to the processing container 1 is performed by thevalve 61 e. By temporarily storing the WCl₆ gas in the storage tank 61 din this way, the gas supply mechanism 5 can stably supply the WCl₆ gasinto the processing container 1 at a relatively large flow rate.

The N₂ gas supply source 62 a supplies an N₂ gas as a purge gas into theprocessing container 1 via a gas supply line 62 b. In the gas supplyline 62 b, a flow rate controller 62 c, a storage tank 62 d and a valve62 e are installed sequentially from the upstream side. On thedownstream side of the valve 62 e, the gas supply line 62 b is connectedto the gas supply line 61 b. The N₂ gas supplied from the N₂ gas supplysource 62 a is temporarily stored in the storage tank 62 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 62 d, and then supplied into the processingcontainer 1. The supply and cutoff of the N₂ gas to be supplied from thestorage tank 62 d to the processing container 1 is performed by thevalve 62 e. By temporarily storing the N₂ gas in the storage tank 62 din this way, the gas supply mechanism 5 can stably supply the N₂ gasinto the processing container 1 at a relatively large flow rate.

The N₂ gas supply source 63 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 63 b. In the gas supplyline 63 b, a flow rate controller 63 c, a valve 63 e and an orifice 63 fare installed sequentially from the upstream side. On the downstreamside of the orifice 63 f, the gas supply line 63 b is connected to thegas supply line 61 b. The N₂ gas supplied from the N₂ gas supply source63 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 63 a to the processing container1 are performed by the valve 63 e. The gas is supplied to the gas supplylines 61 b and 62 b at a relatively large flow rate by the storage tanks61 d and 62 d. The gas supplied to the gas supply lines 61 b and 62 b isprevented from flowing back to the gas supply line 63 b by the orifice63 f.

The H₂ gas supply source 64 a supplies a H₂ gas as a reducing gas intothe processing container 1 via a gas supply line 64 b. In the gas supplyline 64 b, a flow rate controller 64 c, a valve 64 e and an orifice 64 fare installed sequentially from the upstream side. On the downstreamside of the orifice 64 f, the gas supply line 64 b is connected to thegas introduction hole 37. The H₂ gas supplied from the H₂ gas supplysource 64 a is continuously supplied into the processing container 1during the film formation on the wafer W. The supply and cutoff of theH₂ gas to be supplied from the H₂ gas supply source 64 a to theprocessing container 1 are performed by the valve 64 e. The gas issupplied to the gas supply lines 65 b and 66 b at a relatively largeflow rate by the storage tanks 65 d and 66 d which will be describedlater. The gas supplied to the gas supply lines 65 b and 66 b isprevented from flowing back into the gas supply line 64 b by the orifice64 f.

The H₂ gas supply source 65 a supplies a H₂ gas as a reducing gas intothe processing container 1 via a gas supply line 65 b. In the gas supplyline 65 b, a flow rate controller 65 c, a storage tank 65 d and a valve65 e are installed sequentially from the upstream side. On thedownstream side of the valve 65 e, the gas supply line 65 b is connectedto the gas supply line 64 b. The H₂ gas supplied from the H₂ gas supplysource 65 a is temporarily stored in the storage tank 65 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 65 d, and then supplied into the processingcontainer 1. The supply and cutoff of the H₂ gas to be supplied from thestorage tank 65 d to the processing container 1 is performed by thevalve 65 e. By temporarily storing the H₂ gas in the storage tank 65 din this way, the gas supply mechanism 5 can stably supply the H₂ gasinto the processing container 1 at a relatively large flow rate.

The N₂ gas supply source 66 a supplies an N₂ gas as a purge gas into theprocessing container 1 via a gas supply line 66 b. In the gas supplyline 66 b, a flow rate controller 66 c, a storage tank 66 d and a valve66 e are installed sequentially from the upstream side. On thedownstream side of the valve 66 e, the gas supply line 66 b is connectedto the gas supply line 64 b. The N₂ gas supplied from the N₂ gas supplysource 66 a is temporarily stored in the storage tank 66 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 66 d, and then supplied into the processingcontainer 1. The supply and cutoff of the N₂ gas to be supplied from thestorage tank 66 d to the processing container 1 are performed by thevalve 66 e. By temporarily storing the N₂ gas in the storage tank 66 din this manner, the gas supply mechanism 5 can stably supply the N₂ gasinto the processing container 1 at a relatively large flow rate.

The N₂ gas supply source 67 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 67 b. In the gas supplyline 67 b, a flow rate controller 67 c, a valve 67 e and an orifice 67 fare installed sequentially from the upstream side. On the downstreamside of the orifice 67 f, the gas supply line 67 b is connected to thegas supply line 64 b. The N₂ gas supplied from the N₂ gas supply source67 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 67 a to the processing container1 are performed by the valve 67 e. The gas is supplied to the gas supplylines 65 b and 66 b at a relatively large flow rate by the storage tanks65 d and 66 d. The gas supplied to the gas supply lines 65 b and 66 b isprevented from flowing back to the gas supply line 67 b by the orifice67 f.

[Film-Forming Method]

Next, a tungsten film-forming method, which is performed using thefilm-forming system 100 configured as described above, will bedescribed. FIG. 4 is a flowchart showing an example of the flow ofrespective steps of a film-forming method according to an embodiment.FIGS. 5A to 5D are sectional views schematically showing an example ofthe states of a wafer in the respective steps of the film-forming methodaccording to the embodiment.

First, in the film-forming method according to the present embodiment, awafer W (FIG. 5A) having an AlO film as a protective layer formed on thesurface of a silicon film having a recess such as, for example, a trenchor a hole, is prepared. In reality, a recess such as a trench or a hole(contact hole or via hole) is formed in the wafer W. However, for thesake of convenience, the recess is omitted in FIGS. 5A to 5D.

The first film-forming apparatus 101 forms a silicon film on the wafer W(step S1: FIG. 5B). For example, the first film-forming apparatus 101alternately supplies a SiH₄ gas and a B₂H₆ gas into the processingcontainer 1 to form a silicon film (Si (Si—B)). Details of the processof forming the silicon film will be described later.

The second film-forming apparatus 102 supplies a WCl₆ gas and a H₂ gasinto the processing container 1 to form an initial tungsten film (Init.W) on the surface of the wafer W (step S2: FIG. 5C). Details of theprocess of forming the tungsten film will be described later.

The third film-forming apparatus 103 supplies a tungsten-containing gas,for example, a WF₆ gas and a H₂ gas into the processing container 1 toform a main tungsten film (Main W) on the surface of the wafer W (stepS3: FIG. 5D).

[Formation of Silicon Film]

Next, the flow of forming the silicon film by the first film-formingapparatus 101 will be described. FIG. 6 is a diagram showing an exampleof a gas supply sequence at the time of forming the silicon filmaccording to the embodiment.

The control part 6 of the first film-forming apparatus 101 controls theheater 21 of the mounting table 2 to heat the wafer W to a predeterminedtemperature (for example, 250 to 550 degrees C.). Further, the controlpart 6 controls the pressure control valve of the exhaust mechanism 42to regulate the pressure in the processing container 1 to apredetermined pressure (for example, 1.0×10¹ to 1.0×10⁴ Pa).

The control part 6 opens the valves 53 e and 57 e and supplies a carriergas (N₂ gas) at a predetermined flow rate (for example, 100 to 10000sccm) from the N₂ gas supply sources 53 a and 57 a into the processingcontainer 1 via the gas supply lines 53 b and 57 b, respectively. Inparallel with the supply of the carrier gas (N₂ gas) into the processingcontainer 1, the control part 6 supplies a SiH₄ gas and a B₂H₆ gas fromthe SiH₄ gas supply source 51 a and the B₂H₆ gas supply source 55 a tothe gas supply line 51 b and 55 b. Since the valves 51 e and 55 e areclosed, the SiH₄ gas and the B₂H₆ gas are respectively stored in thestorage tanks 51 d and 55 d, and the pressure in the storage tanks 51 dand 55 d is increased. Further, the control part 6 supplies an N₂ gasfrom the N₂ gas supply source 52 a and the N₂ gas supply source 56 a tothe gas supply lines 52 b and 56 b, respectively. Since the valves 52 eand 56 e are closed, the N₂ gas is stored in the storage tanks 52 d and56 d, respectively, and the pressure in the storage tanks 52 d and 56 dis increased.

The control part 6 opens the valve 51 e and supplies the SiH₄ gas storedin the storage tank 51 d into the processing container 1 (step S11).

After a predetermined time (for example, 0.05 to 20 seconds) has elapsedsince the opening of the valve 51 e, the control part 6 closes the valve51 e and stops the supply of the SiH₄ gas into the processing container1. In addition, the control part 6 stops the supply of the SiH₄ gas,opens the valves 52 e and 56 e, and supplies the N₂ gas stored in thestorage tanks 52 d and 56 d into the processing container 1 (step S12).At this time, since the purge gas is supplied from the storage tanks 52d and 56 d having an increased pressure, the purge gas is supplied intothe processing container 1 at a relatively large flow rate, for example,a flow rate (for example, 500 to 10000 sccm) larger than the flow rateof the carrier gas. Therefore, the SiH₄ gas remaining in the processingcontainer 1 is promptly discharged to the exhaust pipe 41, and theinside of the processing container 1 is changed from the SiH₄ gasatmosphere to the atmosphere containing the N₂ gas in a short time. Onthe other hand, as the valve 51 e is closed, the SiH₄ gas supplied fromthe SiH₄ gas supply source 51 a to the gas supply line 516 is stored inthe storage tank 51 d, and the pressure in the storage tank 51 d isincreased.

After a predetermined time (for example, 0.05 to 20 seconds) has elapsedsince the opening of the valves 52 e and 56 e, the control part 6 closesthe valves 52 e and 56 e and stops the supply of the N₂ gas from the gassupply line 52 b and the gas supply line 56 b into the processingcontainer 1. In addition, the control part 6 stops the supply of the N₂gas, opens the valve 55 e, and supplies the B₂H₆ gas stored in thestorage tank 55 d into the processing container 1 (step S13). As aresult, silicon is deposited on the wafer W. As the valve 52 e isclosed, the N₂ gas supplied from the N₂ gas supply source 52 a to thegas supply line 52 b is stored in the storage tank 52 d, and thepressure in the storage tank 52 d is increased. Furthermore, as thevalve 56 e is closed, the N₂ gas supplied from the N₂ gas supply source56 a to the gas supply line 56 b is stored in the storage tank 56 d, andthe pressure in the storage tank 56 d is increased.

After a predetermined time (for example, 0.05 to 20 seconds) has elapsedsince the opening of the valve 55 e, the control part 6 closes the valve55 e and stops the supply of the B₂H₆ gas into the processing container1. In addition, the control part 6 stops the supply of the B₂H₆ gas,opens the valves 52 e and 56 e, and supplies the N₂ gas stored in thestorage tanks 52 d and 56 d into the processing container 1 (step S14).At this time, since the purge gas is supplied from the storage tanks 52d and 56 d having an increased pressure, the purge gas is supplied intothe processing container 1 at a relatively large flow rate, for example,a flow rate (for example, 500 to 10000 sccm) larger than the flow rateof the carrier gas. Therefore, the B₂H₆ gas remaining in the processingcontainer 1 is promptly discharged to the exhaust pipe 41, and theinside of the processing container 1 is changed from the B₂H₆ gasatmosphere to the atmosphere containing the N₂ gas in a short time. Onthe other hand, as the valve 55 e is closed, the B₂H₆ gas supplied fromthe B₂H₆ gas supply source 55 a to the gas supply line 556 is stored inthe storage tank 55 d, and the pressure in the storage tank 55 d isincreased.

After a predetermined time (for example, 0.05 to 20 seconds) has elapsedsince the opening of the valves 52 e and 56 e, the control part 6 closesthe valves 52 e and 56 e and stops the supply of the N₂ gas from the gassupply line 52 b and the gas supply line 56 b into the processingcontainer 1. As the valve 52 e is closed, the N₂ gas supplied from theN₂ gas supply source 52 a to the gas supply line 52 b is stored in thestorage tank 52 d, and the pressure in the storage tank 52 d isincreased. Furthermore, as the valve 56 e is closed, the N₂ gas suppliedfrom the N₂ gas supply source 56 a to the gas supply line 56 b is storedin the storage tank 56 d, and the pressure in the storage tank 56 d isincreased.

The control part 6 forms a silicon film having a desired film thicknessby repeating the cycle of steps S11 to S14 for a plurality of cycles(for example, 10 to 1000 cycles).

The gas supply sequence and the process gas conditions at the time offorming the silicon film shown in FIG. 6 are nothing more than examples,and the present disclosure is not limited thereto. The silicon film maybe formed by using other gas supply sequences and other process gasconditions.

[Formation of Initial Tungsten Film]

Next, a flow of forming an initial tungsten film by the secondfilm-forming apparatus 102 will be described. FIG. 7 is a diagramshowing an example of a gas supply sequence at the time of forming aninitial tungsten film according to an embodiment.

The control part 6 of the second film-forming apparatus 102 controls theheater 21 of the mounting table 2 to heat the wafer W to a predeterminedtemperature (for example, 250 to 650 degrees C.). Further, the controlpart 6 controls the pressure control valve of the exhaust mechanism 42to adjust the pressure in the processing container 1 to a predeterminedpressure (for example, 1.3×10¹ to 8.0×10³ Pa).

The control part 6 opens the valves 63 e and 67 e and supplies a carriergas (N₂ gas) at a predetermined flow rate (for example, 100 to 3000sccm) from the N₂ gas supply sources 63 a and 67 a to the gas supplylines 63 b and 67 b, respectively. Further, the control part 6 opens thevalve 64 e and supplies a H₂ gas at a predetermined flow rate (forexample, 500 to 30000 sccm) from the H₂ gas supply source 64 a to thegas supply line 64 b. Moreover, the control part 6 supplies a WCl₆ gasand a H₂ gas from the WCl₆ gas supply source 61 a and the H₂ gas supplysource 65 a, respectively, to the gas supply lines 61 b and 65 b. Atthis time, since the valves 61 e and 65 e are closed, the WCl₆ gas andthe H₂ gas are respectively stored in the storage tanks 61 d and 65 d,and the pressure in the storage tanks 61 d and 65 d is increased.

Next, the control part 6 opens the valve 61 e, supplies the WCl₆ gasstored in the storage tank 61 d into the processing container 1 as aprecursor, and causes the WCl₆ gas to be adsorbed on the surface of thewafer W (step S21). In parallel with the supply of the WCl₆ gas into theprocessing container 1, the control part 6 supplies a purge gas (N₂ gas)from the N₂ gas supply sources 62 a and 66 a to the gas supply lines 62b and 66 b, respectively. At this time, by closing the valves 62 e and66 e, the purge gas is stored in the storage tanks 62 d and 66 d, andthe pressure in the storage tanks 62 d and 66 d is increased.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valve 61 e, the control part 6 closes the valve61 e. Furthermore, the control part 6 closes the valve 61 e and opensthe valves 62 e and 66 e to stop the supply of the WCl₆ gas into theprocessing container 1 and to supply the purge gas stored in the storagetanks 62 d and 66 d into the processing container 1 (step S22). At thistime, since the purge gas is supplied from the storage tanks 62 d and 66d having an increased pressure, the purge gas is supplied into theprocessing container 1 at a relatively large flow rate, for example, aflow rate (for example, 500 to 10000 sccm) larger than the flow rate ofthe carrier gas. Therefore, the WCl₆ gas remaining in the processingcontainer 1 is promptly discharged to the exhaust pipe 41, and theinside of the processing container 1 is changed from the WCl₆ gasatmosphere to the atmosphere containing the H₂ gas and the N₂ gas in ashort time. On the other hand, as the valve 61 e is closed, the WCl₆ gassupplied from the WCl₆ gas supply source 61 a to the gas supply line 61b is stored in the storage tank 61 d, and the pressure in the storagetank 61 d is increased.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valves 62 e and 66 e, the control part 6 closesthe valves 62 e and 66 e, opens the valve 65 e, and stops the supply ofthe purge gas into the processing container 1. In addition, the controlpart 6 stops the supply of the purge gas, supplies the H₂ gas stored inthe storage tank 65 d into the processing container 1, and reduces theWCl₆ gas adsorbed on the surface of the wafer W (step S23). At thistime, due to the closing of the valves 62 e and 66 e, the purge gassupplied from the N₂ gas supply sources 62 a and 66 a to the gas supplylines 62 b and 66 b, respectively, is stored in the storage tanks 62 dand 66 d, and the pressure in the storage tanks 62 d and 66 d isincreased.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valve 65 e, the control part 6 closes the valve65 e, opens the valves 62 e and 66 e, and stops the supply of the H₂ gasinto the processing container 1. Furthermore, the control part 6 stopsthe supply of the H₂ gas and supplies the purge gas stored in thestorage tanks 62 d and 66 d into the processing container 1 (step S24).At this time, since the purge gas is supplied from the storage tanks 62d and 66 d having an increased pressure, the purge gas is supplied intothe processing container 1 at a relatively large flow rate, for example,a flow rate (for example, 500 to 10000 sccm) larger than the flow rateof the carrier gas. Thus, the H₂ gas remaining in the processingcontainer 1 is promptly discharged to the exhaust pipe 41, and theinside of the processing container 1 is changed from the H₂ gasatmosphere to the atmosphere containing the H₂ gas and the N₂ gas in ashort time. On the other hand, as the valve 65 e is closed, the H₂ gassupplied from the H₂ gas supply source 65 a to the gas supply line 65 bis stored in the storage tank 65 d, and the pressure in the storage tank65 d is increased.

The control part 6 forms an initial tungsten film having a desired filmthickness by repeating the cycle of steps S21 to S24 for a plurality ofcycles (for example, 50 to 2000 cycles).

The gas supply sequence and the process gas conditions at the time offorming the initial tungsten film shown in FIG. 7 are nothing more thanexamples, and the present disclosure is not limited thereto. Thetungsten film may be formed by using other gas supply sequences andother process gas conditions.

[Action and Effect]

Next, the actions and effects of the film-forming method according tothe present embodiment will be described. FIG. 8 is a diagram showing anexample of the layer configuration of the wafer according to the presentembodiment. FIG. 8 shows an example of the layer configuration of thewafer W on which films are formed by the film-forming method accordingto the present embodiment. In the wafer W, an AlO layer as a protectivelayer is formed on a silicon (SiO₂) layer, and a silicon film (Si) isformed on the AlO layer from the viewpoint of adhesion and reactionsuppression. In the wafer W, an initial tungsten film (Init. W) isformed on the silicon film, and a main tungsten film (Main W) is formedon the initial tungsten film, whereby a low-resistance tungsten film isformed.

One example of the process conditions of the film-forming methodaccording to the embodiment will now be summarized below.

Silicon Film

Temperature: 250 to 550 degrees C.

Pressure: 1 to 100 Torr

SiH₄: 100 to 1000 sccm

B₂H₆ gas: 100 to 1000 sccm

Carrier gas (N₂): 100 to 10000 sccm

Purge gas (N₂): 500 to 30000 sccm

Time:

SiH₄ gas: 0.05 to 20 seconds

Purge: 0.05 to 20 seconds

B₂H₆ gas: 0.05 to 20 seconds

Purge: 0.05 to 20 seconds

Initial Tungsten Film

Temperature: 400 to 650 degrees C.

Pressure: 1 to 60 Torr

WCl₆ gas: 50 to 1500 mg/min

Carrier gas (N₂): 100 to 3000 sccm

Purge gas (N₂): 500 to 10000 sccm

H₂ gas: 500 to 30000 sccm

Time:

WCl₆ gas: 0.05 to 5 seconds

Purge: 0.05 to 5 seconds

H₂ gas: 0.05 to 5 seconds

Purge: 0.05 to 5 seconds

Main Tungsten Film

Temperature: 250 to 550 degrees C.

Pressure: 0.1 to 20 Torr

WF₆ gas: 100 to 500 sccm

Carrier gas (N₂): 500 to 10000 sccm

Purge gas (N₂): 0 to 10000 sccm

H₂ gas: 500 to 20000 sccm

Time:

WF₆ gas: 0.05 to 15 seconds

Purge: 0.05 to 15 seconds

H₂ gas: 0.05 to 15 seconds

Purge: 0.05 to 15 seconds

A tungsten film can be formed on the wafer W by forming a silicon filmbefore depositing tungsten. The silicon film may have a thickness ofabout 0.5 to 3 nm in some embodiments. Further, the initial tungstenfilm may have a thickness of about 0.5 to 6 nm. As a result, in thewafer W, grains of tungsten to be deposited can be caused to grow largeand the resistance of the tungsten film can be reduced.

The effects will be described using a comparative example. FIG. 9 is adiagram showing an example of a layer configuration of a wafer accordingto a comparative example. FIG. 9 shows an example of a layerconfiguration of a conventional wafer W. In the wafer W, an AlO layer asa protective layer is formed on a silicon (SiO₂) layer, and a TiN filmhaving a thickness of, for example, 2 nm is formed on the AlO layer fromthe viewpoint of adhesion and reaction suppression. Then, in the waferW, a nucleation step is performed and a tungsten nucleation film (Nuc)having a thickness of, for example, 3 nm is formed on the TiN film.Then, in the wafer W, a low-resistance tungsten film (W) is formed onthe nucleation film.

An example of the process conditions for forming each film of thecomparative example will be described below.

Nucleation Film

Temperature: 250 to 550 degrees C.

Pressure: 1 to 100 Torr

WF₆ gas: 10 to 500 sccm

Carrier gas (N₂): 500 to 10000 sccm

Purge gas (N₂): 0 to 10000 sccm

H₂ gas: 500 to 20000 sccm

SiH₄ gas: 10 to 1000 sccm

Time:

WF₆ gas: 0.05 to 15 seconds

Purge: 0.05 to 15 seconds

SiH₄ gas: 0.05 to 15 seconds

Purge: 0.05 to 15 seconds

Tungsten Film

Temperature: 250 to 550 degrees C.

Pressure: 0.1 to 20 Torr

WF₆ gas: 100 to 500 sccm

Carrier gas (N₂): 1000 to 10000 sccm

Purge gas (N₂): 0 to 10000 sccm

H₂ gas: 500 to 20000 sccm

Time:

WF₆ gas: 0.05 to 15 seconds

Purge: 0.05 to 15 seconds

H₂ gas: 0.05 to 15 seconds

Purge: 0.05 to 15 seconds

FIG. 10 is a diagram showing an example of a change in resistivity withrespect to the thickness of the tungsten film. FIG. 10 shows a change inresistivity depending on the thickness of the tungsten film in the layerconfiguration of the present embodiment shown in FIG. 8 and the layerconfiguration of the comparative example shown in FIG. 9 . In theexample of FIG. 10 , the thickness of the tungsten film is measured fromthe interface with the AlO layer. That is, in the layer configuration ofthe present embodiment, the thickness of the silicon film (Si), theinitial tungsten film (Init. W) and the main tungsten film (Main W) isregarded as the thickness of the tungsten film. In the layerconfiguration of the comparative example, the thickness of the TiN film,the nucleation film (Nuc) and the tungsten film (W) is regarded as thethickness of the tungsten film. In the example of FIG. 10 , there isshown the resistivity normalized with reference to the resistivity ofthe comparative example when the thickness is 10 nm. As shown in FIG. 10, the resistivity of the layer configuration of the present embodimentis lower than that of the comparative example.

Conventionally, when forming a tungsten film on a wafer W, as shown inFIG. 9 , a TiN film is formed as a barrier layer on a silicon layer ofthe wafer W, and a nucleation film is formed on the TiN film. Then, inthe wafer W, a tungsten film (W) is formed on the nucleation film.Conventionally, when forming the tungsten film on the wafer W, thethickness corresponding to the TiN film is also required. In addition,the nucleation film has a high resistance. As the tungsten film isformed thinner, the resistance grows higher. Therefore, in the case ofreducing the thickness of the entire tungsten film, the tungsten filmhas a high resistance due to the influence of the TiN film and thenucleation film.

In the LSI, the wiring is miniaturized, and the reduction in theresistance of the wiring is required. For example, in athree-dimensional stacked semiconductor memory such as a 3D NAND flashmemory or the like, a tungsten film is formed as a word line. For thesake of miniaturization, it is required to further reduce the resistanceof the tungsten film.

On the other hand, in the layer configuration of the present embodiment,it is possible to reduce the resistance of the tungsten film even whenthe thickness of the tungsten film is made small for the purpose ofminiaturization.

In this embodiment, there has been described the case where the initialtungsten film is formed by the combination of the tungsten chloride gasand the hydrogen gas. However, the present disclosure is not limitedthereto. For example, in the second film-forming apparatus 102, theinitial tungsten film may be formed by using only the tungsten chloridegas without using the hydrogen gas. For example, the second film-formingapparatus 102 may intermittently supply only tungsten chloride to forman initial tungsten film. As the tungsten chloride gas, for example, aWCl₆ gas or a WCl₅ gas may be used. Process conditions for forming theinitial tungsten film with the tungsten chloride gas are as follows.

Tungsten Film

Temperature: 400 to 650 degrees C.

Pressure: 1 to 600 Torr

Tungsten chloride gas (WCl₅ or WCl₆): 50 to 1500 mg min

Carrier gas (N₂): 500 to 3000 sccm

Purge gas (N₂): 1000 to 10000 sccm

Time:

Tungsten chloride gas (WCl₅ or WCl₆): 0.05 to 300 seconds

Furthermore, in the present embodiment, there has been described thecase where the silicon film and the initial tungsten film are formed byseparate film-forming apparatuses. However, the present disclosure isnot limited thereto. For example, as shown in FIG. 11 , the siliconfilm, the initial tungsten film and the main tungsten film may be formedby a single film-forming apparatus including a gas supply mechanism forforming a silicon film and a gas supply mechanism for forming a tungstenfilm. Further, the wafer W may be transferred through the respectivefilm-forming apparatuses under the atmospheric pressure.

As described above, in the tungsten film-forming method according to thepresent embodiment, the wafer W having a protective film, for example,an AlO film formed thereon is disposed in the processing container 1,and the silicon film is formed on the wafer W in a reduced pressureatmosphere. In the tungsten film-forming method, the initial tungstenfilm is formed by supplying the tungsten chloride gas to the wafer Whaving the silicon film formed thereon. In the tungsten film-formingmethod, the main tungsten film is formed by supplying thetungsten-containing gas onto the initial tungsten film. This makes itpossible to reduce the resistance of the tungsten film.

Furthermore, in the method of forming the initial tungsten film amongthe tungsten films according to the present embodiment, the tungstenfilm is formed by alternately supplying the tungsten chloride gas andthe hydrogen gas. This makes it possible to quickly form the tungstenfilm.

Moreover, in the tungsten film-forming method according to the presentembodiment, the silicon film is formed by alternately supplying the SiH₄gas and the B₂H₆ gas. This makes it possible to improve the adhesion ofthe silicon film to the wafer W.

In addition, in the tungsten film-forming method according to thepresent embodiment, the film thickness of the silicon film is set to 0.5to 3 nm. This makes it possible to stably form the tungsten film.

Although the embodiment has been described above, various modificationsmay be made without being limited to the above-described embodiment. Forexample, although a semiconductor wafer has been described as an exampleof a substrate, the semiconductor wafer may be silicon, or a compoundsemiconductor such as GaAs, SiC, GaN or the like. Furthermore, thesubstrate is not limited to the semiconductor wafer, but may be a glasssubstrate used for an FPD (flat panel display) such as a liquid crystaldisplay device or the like, a ceramic substrate, and the like.

According to the present disclosure, it is possible to reduce theresistance of a tungsten film.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A film forming system comprising: one or moreprocessing containers; a transfer mechanism configured to load andunload a substrate into and from the one or more processing containers;a gas supply mechanism configured to supply gases to the one or moreprocessing containers; and a controller, wherein the controller controlsthe transfer mechanism and the gas supply mechanism to execute: forminga silicon film on the substrate by disposing the substrate having aprotective film formed on a surface of the substrate in one of the oneor more processing containers, and by alternately supplying a SiH₄ gasand a B₂H₆ gas to the substrate; forming an initial tungsten film on thesilicon film by disposing the substrate having the silicon film formedthereon in one of the one or more processing containers, and bysupplying a tungsten chloride gas to the substrate; and forming a maintungsten film on the initial tungsten film by disposing the substratehaving the silicon film and the initial tungsten film formed thereon inone of the one or more processing containers, and by supplying atungsten-containing gas to the substrate.
 2. The film forming system ofclaim 1, wherein the initial tungsten film is formed by alternatelysupplying the tungsten chloride gas and a hydrogen gas.
 3. The filmforming system of claim 1, wherein the initial tungsten film is formedby supplying the tungsten chloride gas without supplying a hydrogen gas.4. The film forming system of claim 1, wherein the tungsten chloride gasis intermittently supplied.
 5. The film forming system of claim 1,wherein the tungsten chloride gas is WCl₅ or WCl₆.
 6. The film formingsystem of claim 1, wherein the initial tungsten film has a thickness of0.5 to 6 nm.
 7. The film forming system of claim 1, wherein the siliconfilm has a thickness of 0.5 to 3 nm.
 8. The film forming system of claim1, wherein the protective film is an AlO film.
 9. The film formingsystem of claim 1, wherein the silicon film contains boron.
 10. The filmforming system of claim 1, wherein the forming the silicon film and theforming the initial tungsten film are performed in a same processingcontainer among the one or more processing containers.
 11. The filmforming system of claim 1, wherein the forming the initial tungsten filmand the forming the main tungsten film are performed in a sameprocessing container among the one or more processing containers. 12.The film forming system of claim 1, wherein the forming the siliconfilm, the forming the initial tungsten film, and the forming the maintungsten film are performed in a same processing container among the oneor more processing containers.
 13. A film forming system comprising: oneor more processing containers; a transfer mechanism configured to loadand unload a substrate into and from the one or more processingcontainers; a gas supply mechanism configured to supply gases to the oneor more processing containers; and a controller, wherein the controllercontrols the transfer mechanism and the gas supply mechanism to execute:forming a silicon film on the substrate by disposing the substrate inone of the one or more processing containers, and by alternatelysupplying a silicon-containing gas and a B₂H₆ gas to the substrate; andforming a tungsten film on the silicon film by disposing the substratehaving the silicon film formed thereon in one of the one or moreprocessing containers, and by supplying a tungsten-containing gas to thesubstrate, and wherein the silicon-containing gas is SiH₄ or DCS. 14.The film forming system of claim 13, wherein the silicon film containsboron.
 15. The film forming system of claim 13, wherein the forming thesilicon film and the forming the tungsten film are performed indifferent processing containers among the one or more processingcontainers.
 16. The film forming system of claim 13, wherein the formingthe silicon film and the forming the tungsten film are performed in asame processing container among the one or more processing containers.